1. Field of the Invention
The present invention is directed to novel derivatives of 4-sulfanylalkyl-3,5-dinitro benzyl alcohol, i.e. novel compound having sulfanylalkyl group at 4 position of 3,5-dinitro-benzyl alcohol and its preparation method. The novel compound according to the present invention may be used in manufacturing of molecular electronic device.
2. Discussion of Related Art
A molecular electronic device is basically made up of two electrodes and organic molecules covalently bonded to the electrodes, the organic molecule structures function as individual molecule which is separated from the bulk solid state, and the energy level accessible at the molecular state is quantized. Up to the present, the researches on development of organic materials required for the molecular electronic device are concentrated on the materials for molecular wire, molecular switch and molecular rectifier, and the researches have been conducted in developed countries such as America and Europe. Especially, the development of materials for molecular rectifier provided the primitive initiation for the need of development of materials for molecular electronic device. In 1974, Aviram and Ratner of IBM, an American company, proposed at first time that devices having molecular diode rectifying characteristics can be made using the properties of organic molecules, that is, organic molecules themselves have size of nanometer as well as semi-conductive properties at ambient temperature (Chem. Phys. Lett. 1974, 29, 277). They proposed that when a molecule has both of electron donor group(D) and electron acceptor group(A) which are linked through "sgr"-bond, the molecule may be polarized and may have direction, therefore, current will flow to one direction when between a pair of metal electrode, these molecules were aligned in one direction and made an electric circuit. Mattern group approved this hypothesis in 1999 by an experiment for verification of rectifying property of organic LB film formed between two electrodes(Journal of material chemistry, 1999, 9, 2271-75). Furthermore, Metzger group confirmed that compounds linked by xcfx80-bond, as well as "sgr"-bond, also has rectifying property(J. Am. Chem. Soc. 1997, 119, 10455). In addition, professor M. A. Reed, et al of Yale University reported that organic material without electron donor and electron acceptor group may also have rectifying diode property using potential difference of metal(for example, Au and Ti electrode)(Appl. Phys. Lett. 1997, 71, 611).
However, in spite of the variety of researches on development for rectifying diode device using the properties of organic molecules, up to now, the question that whether rectifying property of molecular electronic device is based on the property of organic material or based on other factors is not explained clearly. Thus, there is a request for a development of novel molecular rectifying material by which rectifying property of molecular electronic device can be explained fundamentally. When novel molecular electron accepting organic material is developed and the property of the developed material is measured, it is considered that molecular electronic device having organic material between two electrodes can provide an information on rectifying property and rectifying direction which are depend on the property of the organic material. It is expected that the rectifying property of the organic material can be determined by measuring current-voltage relationship or current flow direction of a device made by forming SAM(self-assembled mono-layer) on one electrode and forming the another electrode on the other side of SAM, or by measuring current-voltage relationship or current flow direction of a SAM using CP-AFM(conducting probe atomic force microscopy) or STM (scanning tunneling microscopy).
However, up to present, there is no report on the organic materials that can attach molecular electron accepting organic material to the electrode. One of the main reasons why there is no such report is the difficulty in synthesis of organic materials for introducing alligator clip to an end of molecular electron acceptor group.
The present invention is directed to novel derivatives of 4-sulfanylalkyl-3,5-dinitro-benzyl alcohol having structure represented by the following formula 1: 
wherein, R is hydrogen, alkyl group, or acetyl group, and n is an integer of 1 to 25. In the novel derivatives of the present invention, to introduce a sulfur atom that is necessary in forming SAM, a sulfanylalkyl group is introduced at 4 position of 3,5-dinitro-benzyl alcohol, which has been used as molecular electron acceptor.
The present invention is also directed to a method for preparing a compound of formula 1, comprising the steps of
a) preparing p-methyl-3,5-dinitro benzoic acid by reacting p-methyl benzoic acid with nitric acid;
b) preparing alkyl 4-methyl-3,5-dinitrobenzoate by reacting said p-methyl-3,5-dinitro benzoic acid with alkyl alcohol in the presence of a catalyst;
c) preparing alkyl 4-halomethyl-3,5-dinitrobenzoate by reacting said alkyl 4-methyl-3,5-dinitrobenzoate with N-halosuccinimide;
d) preparing alkyl 4-halomethyl-3,5-dinitrobenzyl alcohol by converting ester group of alkyl 4-halomethyl-3,5-dinitrobenzoate to alcohol group in the presence of catalyst;
e) preparing compound of following formula wherein R is acetyl group or alkyl group by reacting said alkyl 4-halomethyl-3,5-dinitrobenzyl alcohol with potassium thioacetate or alkylthio sodium, or preparing compound of following formula wherein R is hydrogen by further removing acetyl group or alkyl group.